The Civil Aeronautics Board yesterday proposed to grant airlines the authority to carry passengers between some cities in the United States on their international flights.

Under the board's proposal:

Pan American World Airways would be granted "full-up" rights on its international flights traveling between New York and Washington/Baltimore, New York and Philadelphia, Seattle and Portland, Miami and Tampa, and San Francisco and Los Angeles.

Braniff Airways would get to carry domestic passengers on its Washington/New York, Houston/New Orleans and Los Angeles/San Francisco regiments of international flights.

Northwest Airlines would be granted fill-up rights between San Francisco and Los Angeles.

In another action yesterday, the board awarded major new route authority to four airlines in one of the largest route case decisions in recent years. In granting the carriers new routes, the board turned down the applications of eight other major airlines.

The board granted Braniff Airways a Denver-Oklahoma City-Tampa-Miami/Ft. Lauderdale route as well as a Denver-Oklahoma City-Atlanta Route. Continental Air Lines was awarded a Denver-Tulsa-Tampa-Miami/Ft. Lauderdale route. Delta Air Lines was granted a Atlanta-Tulsa-Denver route. Frontier Airlines was awarded non-stop authority between Denver and Oklahoma City and Denver and Tulsa.

Pan Am had instigated the board's proposal yesterday on "fill-up" rights. The airlines is currently not certificated to carry passengers on flights between the 48 contiguous states. Pan Am unsuccessfully sought domestic routes and fill-up rights for years until last fall when the board awarded it to carry "local" passengers between Detroit and Boston on daily flights bound for and back from London.

Buoyed by that decision, it filed an application for blanket fill-up rights on all its domestic segments, arguing that the board's prohibition was "an archaic, wasteful, and unnecessary restriction."

Pan Am had 1.3 million empty seats in 1975 on flights in its nine domestic segments of international flights. There were 122,600 empty seats on its Washington-New York run during the first eight months of last year alone.

Ten airlines filed in opposition to Pan Am's petition.

The board declined to allow the three carriers the blanket fill-up authority they wanted for all their domestic runs on international flights, however.